Method of manufacture of a radiant plunger electromagnetic ink jet printer

ABSTRACT

This patent describes a method of manufacturing a radiant plunger ink jet print head wherein an array of nozzles are formed on a substrate utilising planar monolithic deposition, lithographic and etching processes. Multiple ink jet heads are formed simultaneously on a single planar substrate such as a silicon wafer. The print heads can be formed utilising standard vlsi/ulsi processing and can include integrated drive electronics formed on the same substrate. The drive electronics preferably being of a CMOS type. In the final construction, ink can be ejected from the substrate substantially normal to the substrate plane.

CROSS REFERENCES TO RELATED APPLICATIONS

The following Australian provisional patent applications are herebyincorporated by cross-reference. For the purposes of location andidentification, U.S. patent applications identified by their U.S. patentapplication serial numbers (USSN) are listed alongside the Australianapplications from which the U.S. patent applications claim the right ofpriority.

CROSS-REFERENCED U.S. patent application AUSTRALIAN (CLAIMING RIGHT OFPRIOR- PROVISIONAL ITY FROM AUSTRALIAN DOCKET PATENT NO. PROVISIONALAPPLICATION) NO. PO7991 09/113,060 ART01 PO8505 09/113,070 ART02 PO798809/113,073 ART03 PO9395 09/112,748 ART04 PO8017 09/112,747 ART06 PO801409/112,776 ART07 PO8025 09/112,750 ART08 PO8032 09/112,746 ART09 PO799909/112,743 ART10 PO7998 09/112,742 ART11 PO8031 09/112,741 ART12 PO803009/112,740 ART13 PO7997 09/112,739 ART15 PO7979 09/113,053 ART16 PO801509/112,738 ART17 PO7978 09/113,067 ART18 PO7982 09/113,063 ART19 PO798909/113,069 ART20 PO8019 09/112,744 ART21 PO7980 09/113,058 ART22 PO801809/112,777 ART24 PO7938 09/113,224 ART25 PO8016 09/112,804 ART26 PO802409/112,805 ART27 PO7940 09/113,072 ART28 PO7939 09/112,785 ART29 PO850109/112,797 PN 6,137,500 ART30 PO8500 09/112,796 ART31 PO7987 09/113,071ART32 PO8022 09/112,824 ART33 PO8497 09/113,090 ART34 PO8020 09/112,823ART38 PO8023 09/113,222 ART39 PO8504 09/112,786 ART42 PO8000 09/113,051ART43 PO7977 09/112,782 ART44 PO7934 09/113,056 ART45 PO7990 09/113,059ART46 PO8499 09/113,091 ART47 PO8502 09/112,753 ART48 PO7981 09/113,055ART50 PO7986 09/113,057 ART51 PO7983 09/113,054 ART52 PO8026 09/112,752ART53 PO8027 09/112,759 ART54 PO8028 09/112,757 ART56 PO9394 09/112,758ART57 PO9396 09/113,107 ART58 PO9397 09/112,829 ART59 PO9398 09/112,792ART60 PO9399 09/112,791 PN 6,106,147 ART61 PO9400 09/112,790 ART62PO9401 09/112,789 ART63 PO9402 09/112,788 ART64 PO9403 09/112,795 ART65PO9405 09/112,749 ART66 PP0959 09/112,784 ART68 PP1397 09/112,783 ART69PP2370 09/112,781 DOT01 PP2371 09/113,052 DOT02 PO8003 09/112,834Fluid01 PO8005 09/113,103 Fluid02 PO9404 09/113,101 Fluid03 PO806609/112,751 IJ01 PO8072 09/112,787 IJ02 PO8040 09/112,802 IJ03 PO807109/112,803 IJ04 PO8047 09/113,697 IJ05 PO8035 09/113,099 IJ06 PO804409/113,084 IJ07 PO8063 09/113,066 IJ08 PO8057 09/112,778 IJ09 PO805609/112,779 IJ10 PO8069 09/113,077 IJ11 PO8049 09/113,061 IJ12 PO803609/112,818 IJ13 PO8048 09/112,816 IJ14 PO8070 09/112,772 IJ15 PO806709/112,819 IJ16 PO8001 09/112,815 IJ17 PO8038 09/113,096 IJ18 PO803309/113,068 IJ19 PO8002 09/113,095 IJ20 PO8068 09/112,808 IJ21 PO806209/112,809 IJ22 PO8034 09/112,780 IJ23 PO8039 09/113,083 IJ24 PO804109/113,121 IJ25 PO8004 09/113,122 IJ26 PO8037 09/112,793 IJ27 PO804309/112,794 IJ28 PO8042 09/113,128 IJ29 PO8064 09/113,127 IJ30 PO938909/112,756 IJ31 PO9391 09/112,755 IJ32 PP0888 09/112,754 IJ33 PP089109/112,811 IJ34 PP0890 09/112,812 IJ35 PP0873 09/112,813 IJ36 *PP099309/112,814 IJ37 PP0890 09/112,764 IJ38 PP1398 09/112,765 IJ39 PP259209/112,767 IJ40 PP2593 09/112,768 IJ41 PP3991 09/112,807 IJ42 PP398709/112,806 IJ43 PP3985 09/112,820 IJ44 PP3983 09/112,821 IJ45 PO793509/112,822 IJM01 PO7936 09/112,825 IJM02 PO7937 09/112,826 IJM03 PO806109/112,827 IJM04 PO8054 09/112,828 IJM05 PO8065 09/113,111 PN 6,071,750IJM06 PO8055 09/113,108 IJM07 PO8053 09/113,109 IJM08 PO8078 09/113,123IJM09 PO7933 09/113,114 IJM10 PO7950 09/1i3,115 IJM11 PO7949 09/113,129IJM12 PO8060 09/113,124 IJM13 PO8059 09/113,125 IJM14 PO8073 09/113,126IJM15 PO8076 09/113,119 IJM16 PO8075 09/113,120 IJM17 PO8079 09/113,221IJM18 PO8050 09/113,116 IJM19 PO8052 09/113,118 IJM20 PO7948 09/113,117IJM21 PO7951 09/113,113 IJM22 PO8074 09/113,130 IJM23 PO7941 09/113,110IJM24 PO8077 09/113,112 IJM25 PO8058 09/113,087 IJM26 PO8051 09/113,074IJM27 PO8045 09/113,089 PN 6,110,754 IJM28 PO7952 09/113,088 IJM29PO8046 09/112,771 IJM30 PO9390 09/112,769 1JM31 PO9392 09/112,770 IJM32PP0889 09/112,798 IJM35 PP0887 09/112,801 IJM36 PP0882 09/112,800 IJM37PP0874 09/112,799 IJM38 PP1396 09/113,098 IJM39 PP3989 09/112,833 IJM40PP2591 09/112,832 IJM41 PP3990 09/112,831 IJM42 PP3986 09/112,830 IJM43PP3984 09/112,836 IJM44 PP3982 09/112,835 IJM45 PP0895 09/113,102 IR01PP0870 09/113,106 IR02 PP0869 09/113,105 IR04 PP0887 09/113,104 IR05PP0885 09/112,810 IR06 PP0884 09/112,766 IR10 PP0886 09/113,085 IR12PP0871 09/113,086 IR13 PP0876 09/113,094 IR14 PP0877 09/112,760 IR16PP0878 09/112,773 IR17 PP0879 09/112,774 IR18 PP0883 09/112,775 IR19PP0880 09/112,745 IR20 PP0881 09/113,092 IR21 PO8006 09/113,100 PN6,087,638 MEMS02 PO8007 09/113,093 MEMS03 PO8008 09/113,062 MEMS04PO8010 09/113,064 PN 6,041,600 MEMS05 PO8011 09/113,082 MEMS06 PO794709/113,081 PN 6,067,797 MEMS07 PO7944 09/113,080 MEMS09 PO794609/113,079 PN 6,044,646 MEMS10 PO9393 09/113,065 MEMS11 PP087509/113,078 MEMS12 PP0894 09/113,075 MEMS13

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the manufacture of ink jet print headsand, in particular, discloses a method of manufacture of a RadiantPlunger Ink Jet Printer.

The present invention further relates to the field of drop on demand inkjet printing.

BACKGROUND OF THE INVENTION

Many ink jet printing mechanisms are known. Unfortunately, in massproduction techniques, the production of ink jet heads is quitedifficult. For example, often, the orifice or nozzle plate isconstructed separately from the ink supply and ink ejection mechanismand bonded to the mechanism at a later stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)). These separate material processing stepsrequired in handling such precision devices often add a substantialexpense in manufacturing.

Additionally, side shooting ink jet technologies (U.S. Pat. No.4,899,181) are often used but again, this limits the amount of massproduction throughput given any particular capital investment.

Additionally, more esoteric techniques are also often utilised. Thesecan include electroforming of nickel stage (Hewlett-Packard Journal,Vol. 36 no 5, pp33-37 (1985)), electro-discharge machining, laserablation (U.S. Pat. No. 5,208,604), micro-punching, etc.

The utilisation of the above techniques is likely to add substantialexpense to the mass production of ink jet print heads and therefore addsubstantially to their final cost.

It would therefore be desirable if an efficient system for the massproduction of ink jet print heads could be developed.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for thecreation of a radiant plunger ink jet printer.

In accordance with a first aspect of the present invention, there isprovided a method of manufacturing a radiant plunger ink jet print headwherein an array of nozzles are formed on a substrate utilising planarmonolithic deposition, lithographic and etching processes. Preferably,multiple ink jet heads are formed simultaneously on a single planarsubstrate such as a silicon wafer.

The print heads can be formed utilising standard vlsi/ulsi processingand can include integrated drive electronics formed on the samesubstrate. The drive electronics preferably are of a CMOS type. In thefinal construction, ink can be ejected from the substrate substantiallynormal to the substrate.

In accordance with a further aspect of the present invention, there isprovided a method of manufacture of an ink jet print head arrangementincluding a series of nozzle chambers, the method comprising the stepsof: (a) utilizing an initial semiconductor wafer having an electricalcircuitry layer and a buried epitaxial layer formed thereon; (b) etchinga nozzle chamber cavity in the wafer, the etching stopping substantiallyat the epitaxial layer; (c) depositing and etching a first layer havinga high saturation flux density on the electrical circuitry layer todefine a first magnetic plate; (d) depositing and etching an insulatinglayer on the first layer and the electrical circuitry layer, the etchingincluding etching vias for a subsequent conductive layer; (e) depositingand etching a conductive layer on the insulating layer in the form of aconductive coil conductively interconnected to the first layer; (f)depositing and etching a sacrificial material layer in the region of thefirst magnetic plate and the coil, the etching including definingapertures for a series of spring posts; (g) depositing and etching asecond layer having a high saturation flux density so as to form aninterconnected second magnetic plate, series of attached springs andspring posts; (h) etching the back of the wafer to the epitaxial layer;(i) etching an ink ejection nozzle through the epitaxial layerinterconnected with the nozzle chamber cavity; and j) etching away anyremaining sacrificial layers.

The step (f) further can comprise etching cavities defining a series ofspring posts and the step (g) preferably can include forming a series ofleaf springs interconnected with the first magnetic plate forresiliently biasing the magnetic plate in a first direction. Theconductive layer can comprise substantially copper.

The etching of layers preferably can include etching vias so as to allowfor the electrical interconnection of portions of subsequently layers.

The magnetic flux material can comprise substantially a cobalt nickeliron alloy and the wafer can comprise a double side polished CMOS wafer.

The steps are preferably also utilized to simultaneously separate thewafer into separate printheads.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of thepresent invention, preferred forms of the invention will now bedescribed, by way of example only, with reference to the accompanyingdrawings which:

FIG. 1 is an exploded perspective view illustrating the construction ofa single ink jet nozzle in accordance with the preferred embodiment ofthe present invention;

FIG. 2 is a timing diagram illustrating the operation of the preferredembodiment;

FIG. 3 is a cross-sectional top view of a single ink nozzle constructedin accordance with the preferred embodiment of the present invention;

FIG. 4 provides a legend of the materials indicated in FIGS. 5 to 21;

FIGS. 5 to 21 illustrate sectional views of the manufacturing steps inone form of construction of an ink jet printhead nozzle;

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In FIG. 1, there is illustrated an exploded perspective viewillustrating the construction of a single ink jet nozzle 4 in accordancewith the principles of the present invention.

The nozzle 4 operates on the principle of electro-mechanical energyconversion and comprises a solenoid 11 which is connected electricallyat a first end 12 to a magnetic plate 13 which is in turn connected to acurrent source eg. 14 utilised to activate the ink nozzle 4. Themagnetic plate 13 can be constructed from electrically conductive iron.

A second magnetic plunger 15 is also provided, again being constructedfrom soft magnetic iron. Upon energising the solenoid 11, the plunger 15is attracted to the fixed magnetic plate 13. The plunger thereby pushesagainst the ink within the nozzle 4 creating a high pressure zone in thenozzle chamber 17. This causes a movement of the ink in the nozzlechamber 17 and in a first design, subsequent ejection of an ink drop. Aseries of apertures eg. 20 is provided so that ink in the region ofsolenoid 11 is squirted out of the holes 20 in the top of the plunger 15as it moves towards lower plate 13. This prevents ink trapped in thearea of solenoid 11 from increasing the pressure on the plunger 15 andthereby increasing the magnetic forces needed to move the plunger 15.

Referring now to FIG. 2, there is illustrated a timing diagram 30 of theplunger current control signal. Initially, a solenoid current pulse 31is activated for the movement of the plunger and ejection of a drop fromthe ink nozzle. After approximately 2 micro-seconds, the current to thesolenoid is turned off. At the same time or at a slightly later time, areverse current pulse 32 is applied having approximately half themagnitude of the forward current. As the plunger has a residualmagnetism, the reverse current pulse 32 causes the plunger to movebackwards towards its original position. A series of torsional springs22, 23 (FIG. 1) also assists in the return of the plunger to itsoriginal position. The reverse current pulse 32 is turned off before themagnetism of the plunger 15 is reversed. which would otherwise result inthe plunger being attracted to the fixed plate 13 again. Returning toFIG. 1, the forced return of the plunger 15 to its quiescent positionresults in a low pressure in the chamber 17. This can cause ink to beginflowing from the outlet nozzle 24 inwards and also ingests air to thechamber 17. The forward velocity of the drop and the backward velocityof the ink in the chamber 17 are resolved by the ink drop breaking offaround the nozzle 24. The ink drop then continues to travel toward therecording medium under its own momentum. The nozzle refills due to thesurface tension of the ink at the nozzle tip 24. Shortly after the timeof drop break off, a meniscus at the nozzle tip is formed with anapproximately concave hemispherical surface. The surface tension willexert a net forward force on the ink which will result in nozzlerefilling. The repetition rate of the nozzle 4 is therefore principallydetermined by the nozzle refill time which will be 100 micro-seconds,depending on the device geometry, ink surface tension and the volume ofthe ejected drop.

Turning now to FIG. 3, an important aspect of the operation of theelectro-magnetically driven print nozzle will now be described. Upon acurrent flowing through the coil 11, the plate 15 becomes stronglyattracted to the plate 13. The plate 15 experiences a downward force andbegins movement towards the plate 13. This movement imparts a momentumto the ink within the nozzle chamber 17. The ink is subsequently ejectedas hereinbefore described. Unfortunately, the movement of the plate 15causes a build-up of pressure in the area 64 between the plate 15 andthe coil 11. This build-up would normally result in a reducedeffectiveness of the plate 15 in ejecting ink.

However, in a first design the plate 15 preferably includes a series ofapertures eg. 20 which allow for the flow of ink from the area 64 backinto the ink chamber and thereby allow a reduction in the pressure inarea 64. This results in an increased effectiveness in the operation ofthe plate 15.

Preferably, the apertures 20 are of a teardrop shape increasing in widthwith increasing radial distance from a center of the plunger. Theaperture profile thereby provides minimal disturbance of the magneticflux through the plunger while maintaining structural integrity ofplunger 15.

After the plunger 15 has reached its end position, the current throughcoil 11 is reversed resulting in a repulsion of the two plates 13, 15.Additionally, the torsional spring eg. 23 acts to return the plate 15 toits initial position.

The use of a torsional spring eg. 23 has a number of substantialbenefits including a compact layout. The construction of the torsionalspring from the same material and same processing steps as that of theplate 15 simplifies the manufacturing process.

In an alternative design, the top surface of plate 15 does not include aseries of apertures. Rather, the inner radial surface 25 (see FIG. 3) ofplate 15 comprises slots of substantially constant cross-sectionalprofile in fluid communication between the nozzle chamber 17 and thearea 64 between plate 15 and the solenoid 11. Upon activation of thecoil 11, the plate 15 is attracted to the armature plate 13 andexperiences a force directed towards plate 13. As a result of themovement, fluid in the area 64 is compressed and experiences a higherpressure than its surrounds. As a result, the flow of fluid takes placeout of the slots in the inner radial surface 25 plate 15 into the nozzlechamber 17. The flow of fluid into chamber 17, in addition to themovement of the plate 15, causes the ejection of ink out of the inknozzle port 24. Again, the movement of the plate 15 causes the torsionalsprings, for example 23, to be resiliently deformed. Upon completion ofthe movement of the plate 15, the coil 11 is deactivated and a slightreverse current is applied. The reverse current acts to repel the plate15 from the armature plate 13. The torsional springs, for example 23,act as additional means to return the plate 15 to its initial orquiescent position.

Fabrication

Returning now to FIG. 1, the nozzle apparatus is constructed from thefollowing main parts including a nozzle surface 40 having an aperture 24which can be constructed from boron doped silicon 50. The radius of theaperture 24 of the nozzle is an important determinant of drop velocityand drop size.

Next, a CMOS silicon layer 42 is provided upon which is fabricated allthe data storage and driving circuitry 41 necessary for the operation ofthe nozzle 4. In this layer a nozzle chamber 17 is also constructed. Thenozzle chamber 17 should be wide enough so that viscous drag from thechamber walls does not significantly increase the force required of theplunger. It should also be deep enough so that any air ingested throughthe nozzle port 24 when the plunger returns to its quiescent state doesnot extend to the plunger device. If it does, the ingested bubble mayform a cylindrical surface instead of a hemispherical surface resultingin the nozzle not refilling properly. A CMOS dielectric and insulatinglayer 44 containing various current paths for the current connection tothe plunger device is also provided.

Next, a fixed plate of ferroelectric material is provided having twoparts 13, 46. The two parts 13, 46 are electrically insulated from oneanother.

Next, a solenoid 11 is provided. This can comprise a spiral coil ofdeposited copper. Preferably a single spiral layer is utilised to avoidfabrication difficulty and copper is used for a low resistivity and highelectro-migration resistance.

Next, a plunger 15 of ferromagnetic material is provided to maximise themagnetic force generated. The plunger 15 and fixed magnetic plate 13, 46surround the solenoid 11 as ;a torus. Thus, little magnetic flux is lostand the flux is concentrated around the gap between the plunger 15 andthe fixed plate 13, 46.

The gap between the fixed plate 13, 46 and the plunger 15 is one of themost important “parts” of the print nozzle 4. The size of the gap willstrongly affect the magnetic force generated, and also limits the travelof the plunger 15. A small gap is desirable to achieve a strong magneticforce, but a large gap is desirable to allow longer plunger 15 travel,and therefore allow a smaller plunger radius to be utilised.

Next, the springs, e.g. 22, 23 for returning to the plunger 15 to itsquiescent position after a drop has been ejected are provided. Thesprings, e.g. 22, 23 can be fabricated from the same material, and inthe same processing steps, as the plunger 15. Preferably the springs,e.g. 22, 23 act as torsional springs in their interaction with theplunger 15.

Finally, all surfaces are coated with passivation layers, which may besilicon nitride (Si₃N₄), diamond like carbon (DLC), or other chemicallyinert, highly impermeable layer. The passivation layers are especiallyimportant for device lifetime, as the active device will be immersed inthe ink.

One form of detailed manufacturing process which can be used tofabricate monolithic ink jet print heads operating in accordance withthe principles taught by the present embodiment can proceed utilizingthe following steps:

1. Using a double sided polished wafer deposit 3 microns of epitaxialsilicon heavily doped with boron 50.

2. Deposit 10 microns of epitaxial silicon 42, either p-type or n-type,depending upon the CMOS process used.

3. Complete a 0.5 micron, one poly, 2 metal CMOS process. This step isshown at 41 in FIG. 5. For clarity, these diagrams may not be to scale,and may not represent a cross section though any single plane of thenozzle. FIG. 4 is a key to representations of various materials in thesemanufacturing diagrams, and those of other cross referenced ink jetconfigurations.

4. Etch the CMOS oxide layers 41 down to silicon or aluminum using Mask1. This mask defines the nozzle chamber, the edges of the print headschips, and the vias for the contacts from the aluminum electrodes to thetwo halves of the split fixed magnetic plate.

5. Plasma etch the silicon 42 down to the boron doped buried layer 50,using oxide from step 4 as a mask. This etch does not substantially etchthe aluminum. This step is shown in FIG. 6.

6. Deposit a seed layer of cobalt nickel iron alloy. CoNiFe is chosendue to a high saturation flux density of 2 Tesla, and a low coercivity.[Osaka, Tetsuya et al, A soft magnetic CoNiFe film with high saturationmagnetic flux density, Nature 392, 796-798 (1998)].

7. Spin on 4 microns of resist 51, expose with Mask 2, and develop. Thismask defines the split fixed magnetic plate, for which the resist actsas an electroplating mold. This step is shown in FIG. 7.

8. Electroplate 3 microns of CoNiFe 52. This step is shown in FIG. 8.

9. Strip the resist 51 and etch the exposed seed layer. This step isshown in FIG. 9.

10. Deposit 0.1 microns of silicon nitride (Si₃N₄).

11. Etch the nitride layer using Mask 3. This mask defines the contactvias from each end of the solenoid coil to the two halves of the splitfixed magnetic plate.

12. Deposit a seed layer of copper. Copper is used for its lowresistivity (which results in higher efficiency) and its highelectromigration resistance, which increases reliability at high currentdensities.

13. Spin on 5 microns of resist 53, expose with Mask 4, and develop.This mask defines the solenoid spiral coil and the spring posts, forwhich the resist acts as an electroplating mold. This step is shown inFIG. 10.

14. Electroplate 4 microns of copper 54.

15. Strip the resist 53 and etch the exposed copper seed layer. Thisstep is shown in FIG. 11.

16. Wafer probe. All electrical connections are complete at this point,bond pads are accessible, and the chips are not yet separated.

17. Deposit 0.1 microns of silicon nitride.

18. Deposit 1 micron of sacrificial material 56. This layer 56determines the magnetic gap.

19. Etch the sacrificial material 56 using Mask 5. This mask defines thespring posts,. This step is shown in FIG. 12.

20. Deposit a seed layer of CoNiFe.

21. Spin on 4.5 microns of resist 57, expose with Mask 6, and develop.This mask defines the walls of the magnetic plunger, plus the springposts. The resist forms an electroplating mold for these parts. Thisstep is shown in FIG. 13.

22. Electroplate 4 microns of CoNiFe 58. This step is shown in FIG. 14.

23. Deposit a seed layer of CoNiFe.

24. Spin on 4 microns of resist 59, expose with Mask 7, and develop.This mask defines the roof of the magnetic plunger, the springs, and thespring posts. The resist forms an electroplating mold for these parts.This step is shown in FIG. 15.

25. Electroplate 3 microns of CoNiFe 60. This step is shown in FIG. 16.

26. Mount the wafer on a glass blank 61 and back-etch the wafer usingKOH, with no mask. This etch thins the wafer and stops at the buriedboron doped silicon layer 50. This step is shown in FIG. 17.

27. Plasma back-etch the boron doped silicon layer 50 to a depth of(approx.) 1 micron using Mask 8. This mask defines the nozzle rim 62.This step is shown in FIG. 18.

28. Plasma back-etch through the boron doped layer using Mask 9. Thismask defines the nozzle, and the edge of the chips. At this stage, thechips are separate, but are still mounted on the glass blank. This stepis shown in FIG. 19.

29. Detach the chips from the glass blank. Strip all adhesive, resist,sacrificial, and exposed seed layers. This step is shown in FIG. 20.

30. Mount the print heads in their packaging, which may be a moldedplastic former incorporating ink channels which supply different colorsof ink to the appropriate regions of the front surface of the wafer.

31. Connect the print heads to their interconnect systems.

32. Hydrophobize the front surface of the print heads.

33. Fill the completed print heads with ink 63 and test them. A fillednozzle is shown in FIG. 21.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present invention asshown in the specific embodiment without departing from the spirit orscope of the invention as broadly described. The present embodiment is,therefore, to be considered in all respects to be illustrative and notrestrictive.

The presently disclosed ink jet printing technology is potentiallysuited to a wide range of printing systems including: color andmonochrome office printers, short run digital printers, high speeddigital printers, offset press supplemental printers, low cost scanningprinters, high speed pagewidth printers, notebook computers within-built pagewidth printers, portable color and monochrome printers,color and monochrome copiers, color and monochrome facsimile machines,combined printer, facsimile and copying machines, label printers, largeformat plotters, photograph copiers, printers for digital photographic‘minilabs’, video printers, PHOTO CD (PHOTO CD is a registered trademark of the Eastman Kodak Company) printers, portable printers for PDAs,wallpaper printers, indoor sign printers, billboard printers, fabricprinters, camera printers and fault tolerant commercial printer arrays.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Ofcourse many different devices could be used. However presently popularink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption.This is approximately 100 times that required for high speed, and stemsfrom the energy-inefficient means of drop ejection. This involves therapid boiling of water to produce a vapor bubble which expels the ink.Water has a very high heat capacity, and must be superheated in thermalink jet applications. This leads to an efficiency of around 0.02%, fromelectricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size andcost. Piezoelectric crystals have a very small deflection at reasonabledrive voltages, and therefore require a large area for each nozzle.Also, each piezoelectric actuator must be connected to its drive circuiton a separate substrate. This is not a significant problem at thecurrent limit of around 300 nozzles per print head, but is a majorimpediment to the fabrication of pagewidth print heads with 19,200nozzles.

Ideally, the ink jet technologies used meet the stringent requirementsof in-camera digital color printing and other high quality, high speed,low cost printing applications. To meet the requirements of digitalphotography, new ink jet technologies have been created. The targetfeatures include:

low power (less than 10 Watts)

high resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systemsdescribed below with differing levels of difficulty. Forty-fivedifferent ink jet technologies have been developed by the Assignee togive a wide range of choices for high volume manufacture. Thesetechnologies form part of separate applications assigned to the presentAssignee as set out in the table above under the heading CROSSREFERENCES TO RELATED APPLICATIONS.

The ink jet designs shown here are suitable for a wide range of digitalprinting systems, from battery powered one-time use digital cameras,through to desktop and network printers, and through to commercialprinting systems

For ease of manufacture using standard process equipment, the print headis designed to be a monolithic 0.5 micron CMOS chip with MEMS postprocessing. For color photographic applications, the print head is 100mm long, with a width which depends upon the ink jet type. The smallestprint head designed is IJ38, which is 0.35 mm wide, giving a chip areaof 35 square mm. The print heads each contain 19,200 nozzles plus dataand control circuitry.

Ink is supplied to the back of the print head by injection moldedplastic ink channels. The molding requires 50 micron features, which canbe created using a lithographically micromachined insert in a standardinjection molding tool. Ink flows through holes etched through the waferto the nozzle chambers fabricated on the front surface of the wafer. Theprint head is connected to the camera circuitry by tape automatedbonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation ofindividual ink jet nozzles have been identified. These characteristicsare largely orthogonal, and so can be elucidated as an elevendimensional matrix. Most of the eleven axes of this matrix includeentries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of inkjet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains36.9 billion possible configurations of ink jet nozzle. While not all ofthe possible combinations result in a viable ink jet technology, manymillion configurations are viable. It is clearly impractical toelucidate all of the possible configurations. Instead, certain ink jettypes have been investigated in detail. These are designated IJ01 toIJ45 which matches the docket numbers in the table under the headingCross References to Related Applications.

Other ink jet configurations can readily be derived from theseforty-five examples by substituting alternative configurations along oneor more of the 11 axes. Most of the IJ01 to IJ45 examples can be madeinto ink jet print heads with characteristics superior to any currentlyavailable ink jet technology.

Where there are prior art examples known to the inventor, one or more ofthese examples are listed in the examples column of the tables below.The IJ01 to IJ45 series are also listed in the examples column. In somecases, a printer may be listed more than once in a table, where itshares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Homeprinters, Office network printers, Short run digital printers,Commercial print systems, Fabric printers, Pocket printers, Internet WWWprinters, Video printers, Medical imaging, Wide format printers,Notebook PC printers, Fax machines, Industrial printing systems,Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrixare set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) DescriptionAdvantages Disadvantages Examples Thermal An electrothermal ♦ Largeforce ♦ High power ♦ Canon Bubblejet bubble heater heats the ink togenerated ♦ ink carrier limited 1979 Endo et al GB above boiling point,♦ Simple to water patent 2,007,162 transferring significant construction♦ Low efficiency ♦ Xerox heater-in- heat to the aqueous ♦ No movingparts ♦ High temperatures pit 1990 Hawkins et ink. A bubble ♦ Fastoperation required al U.S. Pat No. 4,899,181 nucleates and quickly ♦Small chip area ♦ High mechanical ♦ Hewlett-Packard forms, expelling therequired for actuator stress TIJ 1982 Vaught et ink. ♦ Unusual materialsal U.S. Pat No. 4,490,728 The efficiency of the required process is low,with ♦ Large drive typically less than transistors 0.05% of theelectrical ♦ Cavitation causes energy being actuator failure transformedinto ♦ Kogation reduces kinetic energy of the bubble formation drop. ♦Large print heads are difficult to fabricate Piezo- A piezoelectriccrystal ♦ Low power ♦ Very large area ♦ Kyser et al U.S. Pat No.electric such as lead lanthanum consumption required for actuator3,946,398 zirconate (PZT) is ♦ Many ink types ♦ Difficult to ♦ ZoltanU.S. Pat No. electrically activated, can be used integrate with3,683,212 and either ekpands, ♦ Fast operation electronics ♦ 1973 Stemmeshears, or bends to ♦ High efficiency ♦ High voltage U.S. Pat No.3,747,120 apply pressure to the drive transistors ♦ Epson Stylus ink,ejecting drops. required ♦ Tektronix ♦ Full pagewidth ♦ IJ04 print headsimpractical due to actuator size ♦ Requires electrical poling in highfield strengths during manufacture Electro- An electric field is ♦ Lowpower ♦ Low maximum ♦ Seiko Epson, Usui strictive used to activateconsumption strain (approx. et al, JP 253401/96 electrostriction in ♦Many ink types 0.01%) ♦ IJ04 relaxor materials such can be used ♦ Largearea as lead lanthanum ♦ Low thermal required for actuator zirconatetitanate expansion due to low strain (PLZT) or lead ♦ Electric field ♦Response speed is magnesium niobate strength required marginal (˜10 μs)(PMN). (approx. 3.5 V/μm) ♦ High voltage can be generated drivetransistors without difficulty required ♦ Does not require ♦ Fullpagewidth electrical poling print heads impractical due to actuator sizeFerro- An electric field is ♦ Low power ♦ Difficult to ♦ IJ04 electricused to induce a phase consumption integrate with transition between the♦ Many ink types electronics antiferroelectric (AFE) can be used ♦Unusual materials and ferroelectric (FE) ♦ Fast operation such as PLZSnTare phase. Perovskite (<1 μs) required materials such as tin ♦Relatively high ♦ Actuators require modified lead longitudinal strain alarge area lanthanum zirconate ♦ High efficiency titanate (PLZSnT) ♦Electric field exhibit large strains of strength of around 3 up to 1%associated V/μm be readily with the AFE to FE provided phase transition.Electro- Conductive plates are ♦ Low power ♦ Difficult to ♦ IJ02, IJ04static separated by a consumption operate electrostatic platescompressible or fluid ♦ Many ink types devices in an dielectric (usuallyair). can be used aqueous Upon application of a ♦ Fast operationenvironment voltage, the plates ♦ The electrostatic attract each otherand actuator will displace ink, causing normally need to be dropejection. The separated from the conductive plates may ink be in a combor ♦ Very large area honeycomb structure, required to achieve or stackedto increase high forces the surface area and ♦ High voltage thereforethe force. drive transistors may be required ♦ Full pagewidth printheads are not competitive due to actuator size Electro- A strongelectric field ♦ Low current ♦ High voltage ♦ 1989 Saito et al, staticpull is applied to the ink, consumption required U.S. Pat No. 4,799,068on ink whereupon ♦ Low temperature ♦ May be damaged ♦ 1989 Miura et al,electrostatic attraction by sparks due to air U.S. Pat No. 4,810,954accelerates the ink breakdown ♦ Tone-Jet towards the print ♦ Requiredfield medium. strength increases as the drop size decreases ♦ Highvoltage drive transistors required ♦ Electrostatic field attracts dustPermanent An electromagnet ♦ Low power ♦ Complex ♦ IJ07, IJ10 magnetdirectly attracts a consumption fabrication electro- permanent magnet, ♦Many ink types ♦ Permanent magnetic displacing ink and can be usedmagnetic material causing drop ejection. ♦ Fast operation such asNeodymium Rare earth magnets ♦ High efficiency fron Boron (NdFeB) with afield strength ♦ Easy extension required. around 1 Tesla can be fromsingle nozzles ♦ High local used. Examples are: to pagewidth printcurrents required Samarium Cobalt heads ♦ Copper (SaCo) and magneticmetalization should materials in the be used for long neodymium ironboron electromigration family (NdFeB, lifetime and low NdDyFeBNb,resistivity NdDyFeB, etc) ♦ Pigmented inks are usually infeasible ♦Operating temperature limited to the Curie temperature (around 540 K)Soft A solenoid induced a ♦ Low power ♦ Complex ♦ IJ01, IJ05, IJ08,magnetic magnetic field in a soft consumption fabrication IJ10, IJ12,IJ14, core magnetic core or yoke ♦ Many ink types ♦ Materials not IJ15,IJ17 electro- fabricated from a can be used usually present in amagnetic ferrous material such ♦ Fast operation CMOS fab such as aselectroplated iron ♦ High efficiency NiFe, CoNiFe, or alloys such asCoNiFe ♦ Easy extension CoFe are required [1], CoFe, or NiFe from singlenozzles ♦ High local alloys. Typically, the to pagewidth print currentsrequired soft magnetic material heads ♦ Copper is in two parts, whichmetalization should are normally held apart be used for long by aspring. When the electromigration solenoid is actuated, lifetime and lowthe two parts attract, resistivity displacing the ink. ♦ Electroplatingis required ♦ High saturation flux density is required (2.0-2.1 T isachievable with CoNiFe [1]) Lorenz The Lorenz force ♦ Low power ♦ Forceacts as a ♦ IJ06, IJ11, IJ13, force acting on a current consumptiontwisting motion IJ16 carrying wire in a ♦ Many ink types ♦ Typically,only a magnetic field is can be used quarter of the utilized. ♦ Fastoperation solenoid length This allows the ♦ High efficiency providesforce in a magnetic field to be ♦ Easy extension useful directionsupplied externally to from single nozzles ♦ High local the print head,for to pagewidth print currents required example with rare heads ♦Copper earth permanent metalization should magnets. be used for longOnly the current electromigration carrying wire need be lifetime and lowfabricated on the print- resistivity head, simplifying ♦ Pigmented inksmaterials- are usually reguirements. infeasible Magneto- The actuatoruses the ♦ Many ink types ♦ Force acts as a ♦ Fischenbeck, U.S. Pat No.striction giant magnetostrictive can be used twisting motion 4,032,929effect of materials ♦ Fast operation ♦ Unusual materials ♦ IJ25 such asTerfenol-D (an ♦ Easy extension such as Terfenoi-D alloy of terbium,from single nozzles are required dysprosium and iron to pagewidth print♦ High local developed at the Naval heads currents required OrdnanceLaboratory, ♦ High force is ♦ Copper hence Ter-Fe-NOL). availablemetalization should For best efficiency, the be used for long actuatorshoutd be pre- electromigration stressed to approx. 8 lifetime and lowMPa. resistivity ♦ Pre-stressing may be required Surface Ink underpositive ♦ Low power ♦ Requires ♦ Silverbrook, EP tension pressure isheld in a consumption supplementary force 0771 658 A2 and reductionnozzle by surface ♦ Simple to effect drop related patent tension. Thesurface construction separation applications tension of the ink is ♦ Nounusual ♦ Requires special reduced below the materials required in inksurfactants bubble threshold, fabrication ♦ Speed may be causing the inkto ♦ High efficiency limited by surfactant egress from the nozzle. ♦Easy extension properties from single nozzles to pagewidth print headsViscosity The ink viscosity is ♦ Simple ♦ Requires ♦ Silverbrook, EPreduction locally reduced to construction supplementary force 0771 658A2 and select which drops are ♦ No unusual to effect drop related patentto be ejected. A materiais required in separation applications viscosityreduction can fabrication ♦ Requires special be achieved ♦ Easyextension ink viscosity electrothermally with from single nozzlesproperties most inks, but special to pagewidth print ♦ High speed isinks can be engineered heads difficult to achieve for a 100:1 viscosity♦ Requires reduction. oscillating ink pressure ♦ A high temperaturedifference (typically 80 degrees) is required Acoustic An acoustic waveis ♦ Can operate ♦ Complex drive ♦ 1993 Hadimioglu generated andfocussed without a nozzle circuitry et al, EUP 550,192 upon the dropejection plate ♦ Complex ♦ 1993 Elrod et al, region. fabrication EUP572,220 ♦ Low efficiency ♦ Poor control of drop position ♦ Poor controlof drop volume Thermo- An actuator which ♦ Low power ♦ Efficient aqueous♦ IJ03, IJ09, IJ17, elastic relies upon differential consumptionoperation requires a IJ18, IJ19, IJ20, bend thermal expansion ♦ Many inktypes thermal insulator on IJ21, IJ22, IJ23, actuator upon Joule heatingis can be used the hot side IJ24, IJ27, IJ28, used. ♦ Simple planar ♦Corrosion IJ29, IJ30, IJ31, fabrication prevention can be IJ32, IJ33,IJ34, ♦ Small chip area difficult IJ35, IJ36, IJ37, required for each ♦Pigmented inks IJ38 ,IJ39, IJ40, actuator may be infeasible, IJ41 ♦ Fastoperation as pigment particles ♦ High efficiency may jam the bend ♦ CMOSactuator compatible voltages and currents ♦ Standard MEMS processes canbe used ♦ Easy extension from single nozzles to pagewidth print headsHigh CTE A material with a very ♦ High force can be ♦ Requires special ♦IJ09, IJ17, IJ18, thermo- high coefficient of generated material (e.g.PTFE) IJ20, IJ21, IJ22, elastic thermal expansion ♦ Three methods of ♦Requires a PTFE IJ23, IJ24, IJ27, actuator (CTh) such as PTFE depositionare deposition process, IJ28, IJ29, IJ30, polytetrafluoroethylene underdevelopment: which is not yet IJ31, IJ42, IJ43, e (PTFE) is used. Aschemical vapor standard in ULSI IJ44 high CTh materials are deposition(CVD), fabs usually non- spin coating, and ♦ PTFE deposition conductive,a heater evaporation cannot be followed fabricated from a ♦ PTFE is awith high conductive material is candidate for low temperature (aboveincorporated A 50 μm dielectric constant 350° C.) processing long PTFEbend insulation in ULSI ♦ Pigmented inks actuator with ♦ Very low powermay be infeasible, polysilicon heater and consumption as pigmentparticles 15 mW power input ♦ Many ink types may jam the bend canprovide 180 μN can be used actuator force and 10 μm ♦ Simple planardeflection. Actuator fabrication motions include: ♦ Small chip area Bendrequired for each Push actuator Buckle ♦ Fast operation Rotate ♦ Highefficiency ♦ CMOS compatible voltages and currents ♦ Easy extension fromsingle nozzles to pagewidth print heads Conduct- A polymer with a high ♦High force can be ♦ Requires special ♦ IJ24 ive coefficient of thermalgenerated materials polymer expansion (such as ♦ Very low powerdevelopment (High thermo- PTFE) is doped with consumption CTE conductiveelastic conducting substances ♦ Many ink types polymer) actuator toincrease its can be used ♦ Requires a PTFE conductivity to about 3 ♦Simple planar deposition process, orders of magnitude fabrication whichis not yet below that of copper. ♦ Small chip area standard in ULSI Theconducting required for each fabs polymer expands when actuator ♦ PTFEdeposition resistively heated. ♦ Fast operation cannot be followedExamples of ♦ High efficiency with high conducting dopants ♦ CMOStemperature (above include: compatible voltages 350° C.) processingCarbon nanotubes and currents ♦ Evaporation and Metal fibers ♦ Easyextension CVD deposition from single nozzles techniques cannot beConductive polymers to pagewidth print used such as doped heads ♦Pigmented inks polythiophene may be infeasible, Carbon granules aspigment particles may jam the bend actuator Shape A shape memory alloy ♦High force is ♦ Fatigue limits ♦ IJ26 memory such as TiNi (alsoavailable (stresses of maximum number alloy known as Nitinol- hundredsof MPa) of cycles Nickel Titanium alloy ♦ Large strain is ♦ Low strain(1%) developed at the Naval available (more than is required to extendOrdnance Laboratory) 3%) fatigue resistance is thermally switched ♦ Highcorrosion ♦ Cycle rate limited between its weak resistance by heatremoval martensitic state and ♦ Simple ♦ Requires unusual its highstiffness construction materials (TiNi) austenic state. The ♦ Easyextension ♦ The latent heat of shape of the actuator in from singlenozzles transformation must its martensitic state is to pagewidth printbe provided deformed relative to heads ♦ High current the austenicshape. The ♦ Low voltage operation shape change causes operation ♦Requires pre- ejection of a drop. stressing to distort the martensiticstate Linear Linear magnetic ♦ Linear Magnetic ♦ Requires unusual ♦ IJ12Magnetic actuators include the actuators can be semiconductor ActuatorLinear Induction constructed with materials such as Actuator (LIA),Linear high thrust, long soft magnetic alloys Permanent Magnet travel,and high (e.g. CoNiFe) Synchronous Actuator efficiency using ♦ Somevarieties (LPMSA), Linear planar also require Reluctance semiconductorpermanent magnetic Synchronous Actuator fabrication materials such as(LRSA), Linear techniques Neodymium iron Switched Reluctance ♦ Longactuator boron (NdFeB) Actuator (LSRA), and travel is available ♦Requires complex the Linear Stepper ♦ Medium force is multi-phase driveActuator (LSA). available circuitry ♦ Low voltage ♦ High currentoperation operation

BASIC OPERATION MODE Description Advantages Disadvantages ExamplesActuator This is the simplest ♦ Simple operation ♦ Drop repetition ♦Thermal ink jet directly mode of operation: the ♦ No external fieldsrate is usually ♦ Piezoelectric ink pushes ink actuator directlyrequired limited to around 10 jet supplies sufficient ♦ Satellite dropscan kHz. However, this ♦ IJ01, IJ02, IJ03, kinetic energy to expel beavoided if drop is not fundamental IJ04, IJ05, IJ06, the drop. The dropvelocity is less than to the method, but is IJ07, IJ09, IJ11, must havea sufficient 4 m/s related to the refill IJ12, IJ14, IJ16, velocity toovercome ♦ Can be efficient, method normally IJ20, IJ22, IJ23, thesurface tension. depending upon the used IJ24, IJ25, IJ26, actuator used♦ All of the drop IJ27, IJ28, IJ29, kinetic energy must IJ30, IJ31,IJ32, be provided by the IJ33, IJ34, IJ35, actuator IJ36, IJ37, IJ38, ♦Satellite drops IJ39, IJ40, IJ41, usually form if drop IJ42, IJ43, IJ44velocity is greater than 4.5 m/s Proximity The drops to be printed ♦Very simple print ♦ Requires close ♦ Silverbrook, EP are selected bysome head fabrication can proximity between 0771 658 A2 and manner (e.g.thermally be used the print head and related patent induced surface ♦The drop selection the print media or applications tension reduction ofmeans does not need transfer roller pressurized ink). to provide the ♦May require two Selected drops are energy required to print headsprinting separated from the ink separate the drop alternate rows of thein the nozzle by from the nozzle image contact with the print ♦Monolithic color medium or a transfer print heads are roller. difficultElectro- The drops to be printed ♦ Very simple print ♦ Requires very ♦Silverbrook, EP static pull are selected by some head fabrication canhigh electrostatic 0771 658 A2 and on ink manner (e.g. thermally be usedfield related patent induced surface ♦ The drop selection ♦Electrostatic field applications tension reduction of means does notneed for small nozzle ♦ Tone-Jet pressurized ink). to provide the sizesis above air Selected drops are energy required to breakdown separatedfrom the ink separate the drop ♦ Electrostatic field in the nozzle by afrom the nozzle may attract dust strong electric field. Magnetic Thedrops to be printed ♦ Very simple print ♦ Requires ♦ Silverbrook, EPpull on ink are selected by some head fabrication can magnetic ink 0771658 A2 and manner (e.g. thermally be used ♦ Ink colors other relatedpatent induced surface ♦ The drop selection than black are applicationstension reduction of means does not need difficult pressurized ink). toprovide the ♦ Requires very Selected drops are energy required to highmagnetic fields separated from the ink separate the drop in the nozzleby a from the nozzle strong magnetic field acting on the magnetic ink.Shutter The actuator moves a ♦ High speed (>50 ♦ Moving parts are ♦IJ13, IJ17, IJ21 shutter to block ink kHz) operation can required flowto the nozzle. The be achieved due to ♦ Requires ink ink pressure ispulsed reduced refill time pressure modulator at a muitipie of the ♦Drop timing can ♦ Friction and wear drop ejection be very accurate mustbe considered frequency. ♦ The actuator ♦ Stiction is energy can be verypossible low Shuttered The actuator moves a ♦ Actuators with ♦ Movingparts are ♦ IJ08, IJ15, IJ18, grill shutter to block ink small travelcan be required IJ19 flow through a grill to used ♦ Requires ink thenozzle. The shutter ♦ Actuators with pressure modulator movement needonly small force can be ♦ Friction and wear be equal to the width usedmust be considered of the griII holes. ♦ High speed (>50 ♦ Stiction iskHz) operation can possible be achieved Pulsed A pulsed magnetic ♦Extremely low ♦ Requires an ♦ IJ10 magnetic field attracts an ‘inkenergy operation is external pulsed pull on ink pusher’ at the droppossible magnetic field pusher ejection frequency. An ♦ No heat ♦Requires special actuator controls a dissipation problems materials forboth catch, which prevents the actuator and the the ink pusher from inkpusher moving when a drop is ♦ Complex not to be ejected. construction

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description AdvantagesDisadvantages Examples None The actuator directly ♦ Simplicity of ♦ Dropejection ♦ Most ink jets, fires the ink drop, and construction energymust be including there is no external ♦ Simplicity of supplied bypiezoelectric and field or other operation individual nozzie thermalbubble. mechanism required. ♦ Small physical actuator ♦ IJ01, IJ02,IJ03, size IJ04, IJ05, IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23,IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35,IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The inkpressure ♦ Oscillating ink ♦ Requires external ♦ Silverbrook, EP inkoscillates, providing pressure can provide ink pressure 0771 658 A2 andpressure much of the drop a refill pulse, oscillator related patent(including ejection energy. The allowing higher ♦ Ink pressure phaseapplications acoustic actuator selects which operating speed andamplitude must ♦ IJ08, IJ13, IJ15, stimul- drops are to be fired by ♦The actuators may be carefully IJ17, IJ18, IJ19, ation) selectivelyblocking or operate with much controiled IJ21 enabling nozzles. Thelower energy ♦ Acoustic ink pressure oscillation ♦ Acoustic lensesreflections in the ink may be achieved by can be used to focus chambermust be vibrating the print the sound on the designed for head, orpreferably by nozzles an actuator in the ink supply. Media The printhead is ♦ Low power ♦ Precision ♦ Silverbrook, EP proximity placed inclose ♦ High accuracy assembly required 0771 658 A2 and proximity to theprint ♦ Simple print head ♦ Paper fibers may related patent medium.Selected construction cause problems applications drops protrude from ♦Cannot print on the print head further rough substrates than unselecteddrops, and contact the print medium. The drop soaks into the medium fastenough to cause drop separation. Transfer Drops are printed to a ♦ Highaccuracy ♦ Bulky ♦ Silverbrook, EP roller transfer roller instead ♦ Widerange of ♦ Expensive 0771 658 A2 and of straight to the print printsubstrates can ♦ Complex related patent medium. A transfer be usedconstruction applications roller can also be used ♦ Ink can be dried ♦Tektronix hot for proximity drop on the transfer roller meltpiezoelectric separation. ink jet ♦ Any of the IJ series Electro- Anelectric fieId is ♦ Low power ♦ Field strength ♦ Silverbrook, EP staticused to accelerate ♦ Simple print head required for 0771 658 A2 andselected drops towards construction separation of small related patentthe print medium. drops is near or applications above air ♦ Tone-Jetbreakdown Direct A magnetic fleld is ♦ Low power ♦ Requires ♦Silverbrook, EP magnetic used to accelerate ♦ Simple print head magneticink 0771 658 A2 and field selected drops of construction ♦ Requiresstrong related patent magnetic ink towards magnetic field applicationsthe print medium Cross The print head is ♦ Does not require ♦ Requiresexternal ♦ IJ06, IJ16 magnetic placed in a constant magnetic materialsmagnet field magnetic field. The to be integrated in ♦ Current densitiesLorenz force in a the print head may be high, current carrying wiremanufacturing resulting in is used to move the process electromigrationactuator. problems Pulsed A pulsed magnetic ♦ Very low power ♦ Complexprint ♦ IJ10 magnetic field is used to operation is possible headconstruction field cyclically attract a ♦ Small print head ♦ Magneticpaddle, which pushes size materials required in on the ink. A Smallprint head actuator moves a catch, which selectively prevents the paddlefrom moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description AdvantagesDisadvantages Examples None No actuator ♦ Operational ♦ Many actuator ♦Thermal Bubble mechanical simplicity mechanisms have Ink jetamplification is used. insufficient travel, ♦ IJ01, IJ02, IJ06, Theactuator directly or insufficient force, IJ07, IJ16, IJ25, drives thedrop to efficiently drive IJ26 ejection process. the drop ejectionprocess Differential An actuator material ♦ Provides greater ♦ Highstresses are ♦ Piezoelectric expansion expands more on one travel in areduced involved ♦ IJ03, IJ09, IJ17, bend side than on the other. printhead area ♦ Care must be IJ18, IJ19, IJ20, actuator The expansion may betaken that the IJ21, IJ22, IJ23, thermal, piezoelectric, materials donot IJ24, IJ27, IJ29, magnetostrictive, or delaminate IJ30, IJ31, IJ32,other mechanism. The ♦ Residual bend IJ33, IJ34, IJ35, bend actuatorconverts resulting from high IJ36, IJ37, IJ38, a high force low traveltemperature or high IJ39, IJ42, IJ43, actuator mechanism to stressduring IJ44 high travel, lower formation force mechanism. Transient Atrilayer bend ♦ Very good ♦ High stresses are ♦ IJ40, IJ41 bend actuatorwhere the two temperature stability involved actuator outside layers are♦ High speed, as a ♦ Care must be identical. This cancels new drop canbe taken that the bend due to ambient fired before heat materials do nottemperature and dissipates delaminate residual stress. The ♦ Cancelsresidual actuator only responds stress of formation to transient heatingof one side or the other. Reverse The actuator loads a ♦ Better couplingto ♦ Fabrication ♦ IJ05, IJ11 spring spring. When the the ink complexityactuator is turnd off, ♦ High stress in the the spring releases. springThis can reverse the force/distance curve of the actuator to make itcompatible with the force/time requirements of the drop ejection.Actuator A series of thin ♦ Increased travel ♦ Increased ♦ Some stackactuators are stacked. ♦ Reduced drive fabrication piezoelectric inkjets This can be voltage complexity ♦ IJ04 appropriate where ♦ Increasedactuators require high possibility of short electric field strength,circuits due to such as electrostatic pinholes and piezoelectricactuators. Multiple Multiple smaller ♦ Increases the ♦ Actuator forces ♦IJ12, IJ13, IJ18, actuators actuators are used force available from maynot add IJ20, IJ22, IJ28, simultaneously to an actuator linearly,reducing IJ42, IJ43 move the ink. Each ♦ Multiple actuators efficiencyactuator need provide can be positioned to only a portion of the controlink flow force required. accurately Linear A linear spring is used ♦Matches low ♦ Requires print ♦ IJ15 Spring to transform a motion travelactuator with head area for the with small travel and higher travelspring high force into a requirements longer travel, lower ♦ Non-contactforce motion. method of motion transformation Coiled A bend actuator is♦ Increases travel ♦ Generally ♦ IJ17, IJ21, IJ34, actuator coiled toprovide ♦ Reduces chip area restricted to planar IJ35 greater travel ina ♦ Planar implementations due reduced chip area. implementations are toextreme relatively easy to fabrication difficulty fabricate. in otherorientations. Flexure A bend actuator has a ♦ Simple means of ♦ Caremust be ♦ IJ10, IJ19, IJ33 bend small region near the increasing travelof taken not to exceed actuator fixture point, which a bend actuator theelastic limit in flexes much more the flexure area readily than the ♦Stress distribution remainder of the is very uneven actuator. Theactuator ♦ Difficult to flexing is effectively accurately modelconverted from an with finite element even coiling to an analysisangular bend, resulting in greater travel of the actuator tip. Catch Theactuator controls a ♦ Very low actuator ♦ Complex ♦ IJ10 small catch.The catch energy construction either enables or ♦ Very small ♦ Requiresexternal disables movement of actuator size force an ink pusher that is♦ Unsuitable for controlled in a bulk pigmented inks manner. Gears Gearscan be used to ♦ Low force, low ♦ Moving parts are ♦ IJ13 increasetravel at the travel actuators can required expense of duration. be used♦ Several actuator Circular gears, rack ♦ Can be fabricated cycles arerequired and pinion, ratchets, using standard ♦ More complex and othergearing surface MEMS drive electronics methods can be used. processes ♦Complex construction ♦ Friction, friction, and wear are possible BuckleA buckle plate can be ♦ Very fast ♦ Must stay within ♦ S. Hirata et al,plate used to change a slow movement elastic limits of the “An Ink-jetHead actuator into a fast achievable materials for long Using Diaphragmmotion. It can also device life Microactuator”, convert a high force, ♦High stresses Proc. IEEE MEMS, low travel actuator into involved Feb.1996, pp 418- a high travel, medium ♦ Generally high 423. force motion.power requirement ♦ IJ18, IJ27 Tapered A tapered magnetic ♦ Linearizesthe ♦ Complex ♦ IJ14 magnetic pole can increase magnetic constructionpole travel at the expense of force/distance curve force. Lever A leverand fulcrum is ♦ Matches low ♦ High stress ♦ IJ32, IJ36, IJ37 used totransform a travel actuator with around the fulcrum motion with smallhigher travel travel and high force requirements into a motion with ♦Fulcrum area has longer travel and lower no linear movement, force. Thelever can and can be used for also reverse the a fluid seal direction oftravel. Rotary The actuator is ♦ High mechanical ♦ Complex ♦ IJ28impeller connected to a rotary advantage construction impeller. A small♦ The ratio of force ♦ Unsuitable for angular deflection of to travel ofthe pigmented inks the actuator results in a actuator can be rotation ofthe impeller matched to the vanes, which push the nozzle requirementsink against stationary by varying the vanes and out of the number ofimpeller nozzle. vanes Acoustic A refractive or ♦ No moving parts ♦Large area ♦ 1993 Hadimioglu lens diffractive (e.g. zone required et al,EUP 550,192 plate) acoustic lens is ♦ Only relevant for ♦ 1993 Elrod etal, used to concentrate acoustic ink jets EUP 572,220 sound waves. SharpA sharp point is used ♦ Simple ♦ Difficult to ♦ Tone-jet conductive toconcentrate an construction fabricate using point electrostatic field.standard VLSI processes for a surface ejecting ink- jet ♦ Only relevantfor electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume Thevolume of the ♦ Simple ♦ High energy is ♦ Hewlett-Packard expansionactuator changes, construction in the typically required to Thermal Inkjet pushing the ink in all case of thermal ink achieve volume ♦ CanonBubblejet directions. jet expansion. This leads to thermal stress,cavitation, and kogation in thermal ink jet implementations Linear, Theactuator moves in ♦ Efficient coupling ♦ High fabrication ♦ IJ01, IJ02,IJ04, normal to a direction normal to to ink drops ejected complexitymay be IJ07, IJ11, IJ14 chip the print head surface. normal to therequired to achieve surface The nozzle is typically surfaceperpendicular in the line of motion movement. Parallel to The actuatormoves ♦ Suitable for planar ♦ Fabrication ♦ IJ12, IJ13, IJ15, chipparallel to the print fabrication complexity IJ33, IJ34, IJ35, surfacehead surface. Drop ♦ Friction IJ36 ejection may still be ♦ Stictionnormal to the surface. Membrane An actuator with a ♦ The effective area♦ Fabrication ♦ 1982 Howkins push high force but small of the actuatorcomplexity U.S. Pat. No. 4,459,601 area is used to push a becomes the ♦Actuator size stiff membrane that is membrane area ♦ Difficulty of incontact with the ink. integration in a VLSI process Rotary The actuatorcauses ♦ Rotary levers may ♦ Device ♦ IJ05, IJ08, IJ13, the rotation ofsome be used to increase complexity IJ28 element, such a grill or travel♦ May have friction impeller ♦ Small chip area at a pivot pointrequirements Bend The actuator bends ♦ A very small ♦ Requires the ♦1970 Kyser et al when energized. This change in actuator to be made U.S.Pat. No. 3,946,398 may be due to dimensions can be from at least two ♦1973 Stemme differential thermal converted to a large distinct layers,or to U.S. Pat. No. 3,747,120 expansion, motion. have a thermal ♦ IJ03,IJ09, IJ10, piezoelectric difference across the IJ19, IJ23, IJ24,expansion, actuator IJ25, IJ29, IJ30, magnetostriction, or IJ31, IJ33,IJ34, other form of relative IJ35 dimensional change. Swivel Theactuator swivels ♦ Allows operation ♦ Inefficient ♦ IJ06 around acentral pivot. where the net linear coupling to the ink This motion issuitable force on the paddle motion where there are is zero oppositeforces applied ♦ Small chip area to opposite sides of the requirementspaddle, e.g. Lorenz force. Straighten The actuator is ♦ Can be used with♦ Requires careful ♦ IJ26, IJ32 normally bent, and shape memory balanceof stresses straightens when alloys where the to ensure that theenergized. austenic phase is quiescent bend is planar accurate DoubleThe actuator bends in ♦ One actuator can ♦ Difficult to make ♦ IJ36,IJ37, IJ38 bend one direction when be used to power the drops ejected byone element is two nozzles. both bend directions energized, and bends ♦Reduced chip identical. the other way when size. ♦ A small efficiencyanother element is ♦ Not sensitive to loss compared to energized.ambient temperature equivalent single bend actuators. Shear Energizingthe actuator ♦ Can increase the ♦ Not readily ♦ 1985 Fishbeck causes ashear motion effective travel of applicable to other U.S. Pat. No.4,584,590 in the actuator piezoelectric actuator material. actuatorsmechanisms Radial The actuator squeezes ♦ Relatively easy to ♦ Highforce ♦ 1970 Zoltan U.S. Pat. No. con- an ink reservoir, fabricatesingle required 3,683,212 striction forcing ink from a nozzles fromglass ♦ Inefficient constricted nozzle. tubing as ♦ Difficult tomacroscopic integrate with VLSI structures processes Coil/ A coiledactuator ♦ Easy to fabricate ♦ Difficult to ♦ IJ17, IJ21, IJ34, uncoiluncoils or coils more as a planar VLSI fabricate for non- IJ35 tightly.The motion of process planar devices the free end of the ♦ Small area ♦Poor out-of-plane actuator ejects the ink. required, therefore stiffnesslow cost Bow The actuator bows (or ♦ Can increase the ♦ Maximum travel ♦IJ16, IJ18, IJ27 buckles) in the middle speed of travel is constrainedwhen energized. ♦ Mechanically ♦ High force rigid required Push-Pull Twoactuators control ♦ The structure is ♦ Not readily ♦ IJ18 a shutter. Oneactuator pinned at both ends, suitable for ink jets pulls the shutter,and so has a high out-of- which directly push the other pushes it. planerigidity the ink Curl A set of actuators curl ♦ Good fluid flow to ♦Design ♦ IJ20, IJ42 inwards inwards to reduce the the region behindcomplexity volume of ink that they the actuator enclose. increasesefficiency Curl A set of actuators curl ♦ Relatively simple ♦ Relativelylarge ♦ IJ43 outwards outwards, pressurizing construction chip area inkin a chamber surrounding the actuators, and expelling ink from a nozzlein the chamber. Iris Multiple vanes enclose ♦ High efficiency ♦ Highfabrication ♦ IJ22 a volume of ink. These ♦ Small chip area complexitysimultaneously rotate, ♦ Not suitable for reducing the volume pigmentedinks between the vanes. Acoustic The actuator vibrates ♦ The actuatorcan ♦ Large area ♦ 1993 Hadimioglu vibration at a high frequency. bephysically distant required for efficient et al, EUP 550,192 from theink operation at useful ♦ 1993 Elrod et al, frequencies EUP 572,220 ♦Acoustic coupling and crosstalk ♦ Complex drive circuitry ♦ Poor controlof drop volume and position None In various ink jet ♦ No moving parts ♦Various other ♦ Silverbrook, EP designs the actuator tradeoffs are 0771658 A2 and does not move. required to eliminate related patent movingparts applications ♦ Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages ExamplesSurface This is the normal way ♦ Fabrication ♦ Low speed ♦ Thermal inkjet tension that ink jets are simplicity ♦ Surface tension ♦Piezoelectric ink refilled. After the ♦ Operational force relatively jetactuator is energized, simplicity small compared to ♦ IJ01-IJ07, IJ10-it typically returns actuator force IJ14, IJ16, IJ20, rapidly to itsnormal ♦ Long refill time IJ22-IJ45 position. This rapid usuallydominates return sucks in air the total repetition through the nozzlerate opening. The ink surface tension at the nozzle then exerts a smallforce restoring the meniscus to a minimum area. This force refills thenozzle. Shuttered Ink to the nozzle ♦ High speed ♦ Requires common ♦IJ08, IJ13, IJ15, oscillating chamber is provided at ♦ Low actuator inkpressure IJ17, IJ18, IJ19, ink a pressure that energy, as the oscillatorIJ21 pressure oscillates at twice the actuator need only ♦ May not bedrop ejection open or close the suitable for frequency. When a shutter,instead of pigmented inks drop is to be ejected, ejecting the ink dropthe shutter is opened for 3 half cycles: drop ejection, actuator return,and refill. The shutter is then closed to prevent the nozzle chamberemptying during the next negative pressure cycle. Refill After the mainactuator ♦ High speed, as the ♦ Requires two ♦ IJ09 actuator has ejecteda drop a nozzle is actively independent second (refill) actuatorrefilled actuators per nozzle is energized. The refill actuator pushesink into the nozzie chamber. The refill actuator returns slowly, toprevent its return from emptying the chamber again. Positive The ink isheld a slight ♦ High refill rate, ♦ Surface spill must ♦ Silverbrook, EPink positive pressure. therefore a high be prevented 0771 658 A2 andpressure After the ink drop is drop repetition rate ♦ Highly relatedpatent ejected, the nozzle is possible hydrophobic print applicationschamber fills quickly head surfaces are ♦ Alternative for:, as surfacetension and required IJ01-IJ07, IJ10-IJ14, ink pressure both IJ16, IJ20,IJ22-1145 operate to refill the nozzle

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description AdvantagesDisadvantages Examples Long inlet The ink inlet channel ♦ Designsimplicity ♦ Restricts refill ♦ Thermal ink jet channel to the nozzlechamber ♦ Operational rate ♦ Piezoelectric ink is made long andsimplicity ♦ May result in a jet relatively narrow, ♦ Reduces crosstalkrelatively large chip ♦ IJ42, IJ43 relying on viscous drag area toreduce inlet back- ♦ Only partially flow. effective Positive The ink isunder a ♦ Drop selection ♦ Requires a ♦ Silverbrook, EP ink positivepressure, so and separation method (such as a 0771 658 A2 and pressurethat in the quiescent forces can be nozzle rim or related patent statesome of the ink reduced effective applications drop already protrudes ♦Fast refill time hydrophobizing, or ♦ Possible operation from thenozzle. both) to prevent of the following: This reduces the flooding ofthe IJ01-IJ07, IJ09- pressure in the nozzle ejection surface of IJ12,IJ14, IJ16, chamber which is the print head. IJ20, IJ22, IJ23- requiredto eject a IJ34, IJ36-IJ41, certain volume of ink. IJ44 The reduction inchamber pressure results in a reduction in ink pushed out through theinlet. Baffle One or more baffles ♦ The refill rate is ♦ Design ♦ HPThermal Ink are placed in the inlet not as restricted as complexity Jetink flow. When the the long inlet ♦ May increase ♦ Tektronix actuator isenergized, method. fabrication piezoelectric ink jet the rapid ink ♦Reduces crosstalk complexity (e.g. movement creates Tektronix hot melteddies which restrict Piezoelectric print the flow through the heads).inlet. The slower refill process is unrestricted, and does not result ineddies. Flexible In this method recently ♦ Significantly ♦ Notapplicable to ♦ Canon flap disclosed by Canon, reduces back-flow mostink jet restricts the expanding actuator for edge-shooter configurationsinlet (bubble) pushes on a thermal inkjet ♦ Increased flexible flap thatdevices fabrication restricts the inlet. complexity ♦ Inelasticdeformation of polymer flap results in creep over extended use Inletfilter A filter is located ♦ Additional ♦ Restricts refill ♦ IJ04, IJ12,IJ24, between the ink inlet advantage of ink rate IJ27, IJ29, IJ30 andthe nozzle filtration ♦ May result in chamber. The filter has ♦ Inkfllter may be complex a multitude of small fabricated with noconstruction holes or slots, additional process restricting ink flow.steps The filter also removes particles which may block the nozzle.Small inlet The ink inlet channel ♦ Design simplicity ♦ Restricts refill♦ IJ02, IJ37, IJ44 compared to the nozzle chamber rate to nozzle has asubstantially ♦ May result in a smaller cross section relatively largechip than that of the nozzle area resulting in easier ink ♦ Onlypartially egress out of the effective nozzle than out of the inlet.Inlet A secondary actuator ♦ Increases speed of ♦ Requires separate ♦IJ09 shutter controls the position of the ink-jet print head refillactuator and a shutter, closing off operation drive circuit the inkinlet when the main actuator is energized. The inlet The method avoidsthe ♦ Back-flow ♦ Requires careful ♦ IJ01, IJ03, IJ05, is locatedproblem of inlet back- problem is design to minimize IJ06, IJ07, IJ10,behind the flow by arranging the eliminated the negative IJ11, IJ14,IJ16, ink- ink-pushing surface of pressure behind the IJ22, IJ23, IJ25,pushing the actuator between paddle IJ28, IJ31, IJ32, surface the inletand the IJ33, IJ34, IJ35, nozzle. 1136, IJ39, IJ40, IJ41 Part of the Theactuator and a ♦ Significant ♦ Small increase in ♦ IJ07, IJ20, IJ26,actuator wall of the ink reductions in back- fabricatidn IJ38 moves tochamber are arranged flow can be complexity shut off so that the motionof achieved the inlet the actuator closes off ♦ Compact designs theinlet. possible Nozzle In some configurations ♦ Ink back-flow ♦ Nonerelated to ♦ Silverbrook, EP actuator of inkjet, there is no problem isink back-flow on 0771 658 A2 and does not expansion or eliminatedactuation related patent result in movement of an applications ink back-actuator which may ♦ Valve-jet flow cause ink back-flow ♦ Tone-jetthrough the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages ExamplesNormal All of the nozzles are ♦ No added ♦ May not be ♦ Most ink jetnozzle fired periodically, complexity on the sufficient to displacesystems firing before the ink has a print head dried ink ♦ IJ01, IJ02,IJ03, chance to dry. When IJ04, IJ05, IJ06, not in use the nozzles IJ07,IJ09, IJ10, are sealed (capped) IJ11, IJ12, IJ14, against air. IJ16,IJ20, IJ22, The nozzle firing is IJ23, IJ24, IJ25, usually performedIJ26, IJ27, IJ28, during a special IJ29, IJ30, IJ31, clearing cycle,after IJ32, IJ33, IJ34, first moving the print IJ36, IJ37, IJ38, head toa cleaning IJ39, IJ40, IJ41, station. IJ42, IJ43, IJ44,, IJ45 Extra Insystems which heat ♦ Can be highly ♦ Requires higher ♦ Silverbrook, EPpower to the ink, but do not boil effective if the drive voltage for0771 658 A2 and ink heater it under normal heater is adjacent toclearing related patent situations, nozzle the nozzle ♦ May requireapplications clearing can be larger drive achieved by over- transistorspowering the heater and boiling ink at the nozzle. Rapid The actuator isfired in ♦ Does not require ♦ Effectiveness ♦ May be used with: success-rapid succession. In extra drive circuits depends IJ0I, IJ02, IJ03, ionof some configurations, on the print head substantially upon IJ04, IJ05,IJ06, actuator this may cause heat ♦ Can be readily the conflguration ofIJ07, IJ09, IJ10, pulses build-up at the nozzle controlled and theinkjet nozzle IJ11, IJ14, IJ16, which boils the ink, initiated bydigital IJ20, IJ22, IJ23, clearing the nozzle. In logic IJ24, IJ25,IJ27, other situations, it may IJ28, IJ29, IJ30, cause sufficient IJ31,IJ32, IJ33, vibrations to dislodge IJ34, IJ36, IJ37, clogged nozzles.IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44, IJ45 Extra Where an actuatoris ♦ A simple solution ♦ Not suitable ♦ May be used with: power to notnormally driven to where applicable where there is a hard IJ03, IJ09,IJ16, ink the limit of its motion, limit to actuator IJ20, IJ23, IJ24,pushing nozzle clearing may be movement IJ25, IJ27, IJ29, actuatorassisted by providing IJ30, IJ31, IJ32, an enhanced drive IJ39, IJ40,IJ41, signal to the actuator. IJ42, IJ43, IJ44, IJ45 Acoustic Anultrasonic wave is ♦ A high nozzle ♦ High ♦ IJ08, IJ13, IJ15, resonanceapplied to the ink clearing capability implementation cost IJ17, IJ18,IJ19, chamber. This wave is can be achieved if system does not IJ21 ofan appropriate ♦ May be already include an amplitude and implemented atvery acoustic actuator frequency to cause low cost in systems sufficientforce at the which already nozzle to clear include acoustic blockages.This is actuators easiest to achieve if the ultrasonic wave is at aresonant frequency of the ink cavity. Nozzle A microfabricated ♦ Canclear severely ♦ Accurate ♦ Silverbrook, EP clearing plate is pushedagainst clogged nozzles mechanical 0771 658 A2 and plate the nozzles.The plate alignment is related patent has a post for every requiredapplications nozzle. A post moves ♦ Moving parts are through eachnozzle, required displacing dried ink. ♦ There is risk of damage to thenozzles ♦ Accurate fabrication is required Ink The pressure of the ink ♦May be effective ♦ Requires pressure ♦ May be used with pressure istemporarily where other pump or other all IJ series ink jets pulseincreased so that ink methods cannot be pressure actuator streams fromall of the used ♦ Expensive nozzles. This may be ♦ Wasteful of ink usedin conjunction with actuator energizing. Print head A flexible ‘blade’is ♦ Effective for ♦ Difficult to use if ♦ Many ink jet wiper wipedacross the print planar print head print head surface is systems headsurface. The surfaces non-planar or very blade is usually ♦ Low costfragile fabricated from a ♦ Requires flexible polymer, e.g. mechanicalparts rubber or synthetic ♦ Blade can wear elastomer. out in high volumeSeparate A separate heater is ♦ Can be effective ♦ Fabrication ♦ Can beused with ink boiling provided at the nozzle where other nozzlecomplexity many IJ series ink heater although the normal clearingmethods jets drop e-ection cannot be used mechanism does not ♦ Can berequire it. The heaters implemented at no do not require additional costin individual drive some ink jet circuits, as many configurationsnozzles can be cleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages ExamplesElectro- A nozzle plate is ♦ Fabrication ♦ High temperatures ♦ HewlettPackard formed separately fabricated simplicity and pressures areThermal Ink jet nickel from electroformed required to bond nickel, andbonded to nozzle plate the print head chip. ♦ Minimum thicknessconstraints ♦ Differential thermal expansion Laser Individual nozzleholes ♦ No masks ♦ Each hole must be ♦ Canon Bubblejet ablated or areablated by an required individually formed ♦ 1988 Sercel et al., drilledintense UV laser in a ♦ Can be quite fast ♦ Special equipment SPIE, Vol.998 polymer nozzle plate, which is ♦ Some control over required ExcimerBeam typically a polymer nozzle profile is ♦ Slow where thereApplications, pp. such as polyimide or possible are many thousands 76-83polysulphone ♦ Equipment of nozzle per print ♦ 1993 Watanabe et requiredis relatively head al., U.S. Pat. No. low cost ♦ May produce thin5,208,604 burrs at exit holes Silicon A separate nozzle plate ♦ Highaccuracy is ♦ Two part ♦ K. Bean, IEEE micro- is micromachinedattainable construction Transactions on machined from single crystal ♦High cost Electron Devices, silicon, and bonded to ♦ Requires precisionVol. ED-25, No. 10, the print head wafer. alignment 1978, pp 1185-1195 ♦Nozzles may be ♦ Xerox 1990 clogged by adhesive Hawkins et al., U.S.Pat. No. 4,899,181 Glass Fine glass capillaries ♦ No expensive ♦ Verysmall nozzle ♦ 1970 Zoltan U.S. capillaries are drawn from glassequipment required sizes are difficult to Pat. No. 3,683,212 tubing.This method ♦ Simple to make form has heen used for single nozzles ♦ Notsuited for making individual mass production nozzle, but is difficult touse for bulk manufacturing of print heads with thousands of nozzles.Monolithic, The nozzle plate is ♦ High accuracy (<1 ♦ Requires ♦Silverbrook, EP surface deposited as a layer μm) sacrificial layer 0771658 A2 and micro- using standard VLSI ♦ Monolithic under the nozzlerelated patent machined deposition techniques. ♦ Low cost plate to formthe applications using VLSI Nozzles are etched in ♦ Existing processesnozzle chamber ♦ IJ01, IJ02, IJ04, litho- the nozzle plate using can beused ♦ Surface may be IJ11, IJ12, IJ17, graphic VLSI lithography andfragile to the touch IJ18, IJ20, IJ22, processes etching. IJ24, IJ27,IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40,IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is a ♦ High accuracy(<1 ♦ Requires long ♦ IJ03, IJ05, IJ06, etched buried etch stop jn theμm) etch times IJ07, IJ08, IJ09, through wafer. Nozzle ♦ Monolithic ♦Requires a IJ10, IJ13, IJ14, substrate chambers are etched in ♦ Low costsupport wafer IJ15, IJ16, IJ19, the front of the wafer, ♦ Nodifferential IJ21, IJ23, IJ25, and the wafer is expansion IJ26 thinnedfrom the back side. Nozzles are then etched in the etch stop layer. Nonozzle Various methods have ♦ No nozzles to ♦ Difficult to ♦ Ricoh 1995plate been tried to eliminate become clogged control drop positionSekiya et al U.S. the nozzles entirely, to accurately Pat. No. 5,412,413prevent nozzle ♦ Crosstalk ♦ 1993 Hadimioglu clogging. These problems etal EUP 550,192 include thermal bubble ♦ 1993 Elrod et al mechanisms andEUP 572,220 acoustic lens mechanisms Trough Each drop ejector has ♦Reduced ♦ Drop firing ♦ IJ35 a trough through which manufacturingdirection is sensitive a paddle moves. There complexity to wicking. isno nozzle plate. ♦ Monolithic Nozzle slit The elimination of ♦ Nonozzles to ♦ Difficult to ♦ 1989 Saito et al instead of nozzle holes andbecome clogged control drop position U.S. Pat. No. 4,799,068 individualreplacement by a slit accurately nozzles encompassing many ♦ Crosstalkactuator positions problems reduces nozzle clogging, but increasescrosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages ExamplesEdge Ink flow is along the ♦ Simple ♦ Nozzles limited to ♦ CanonBubblejet (‘edge surface of the chip, construction edge 1979 Endo et alGB shooter’) and ink drops are ♦ No silicon etching ♦ High resolution ispatent 2,007,162 ejected from the chip required difficult ♦ Xeroxheater-in- edge. ♦ Good heat sinking ♦ Fast color printing pit 1990Hawkins et via substrate requires one print al U.S. Pat. No. 4,899,181 ♦Mechanically head per color ♦ Tone-jet strong ♦ Ease of chip handingSurface Ink flow is along the ♦ No bulk silicon ♦ Maximum ink ♦Hewlett-Packard (‘roof surface of the chip, etching required flow isseverely TIJ 1982 Vaught et shooter’) and ink drops are ♦ Silicon canmake restricted al U.S. Pat. No. 4,490,728 ejected from the chip aneffective heat ♦ IJ02, IJ11, IJ12, surface, normal to the sink IJ20,IJ22 plane of the chip. ♦ Mechanical strength Through Ink flow isthrough the ♦ High ink flow ♦ Requiresbulk ♦ Silverbrook, EP chip, chip,and ink drops are ♦ Suitable for silicon etching 0771 658 A2 and forwardejected from the front pagewidth print related patent (‘up surface ofthe chip. heads applications shooter’) ♦ High nozzle ♦ IJ04, IJ17, IJ18,packing density IJ24, IJ27-IJ45 therefore low manufacturing cost ThroughInk flow is through the ♦ High ink flow ♦ Requires wafer ♦ IJ01, IJ03,IJ05, chip, chip, and ink drops are ♦ Suitable for thinning IJ06, IJ07,IJ08, reverse ejected from the rear pagewidth print ♦ Requires specialIJ09, IJ10, IJ13, (‘down surface of the chip. heads handling duringIJ14, IJ15, IJ16, shooter’) ♦ High nozzle manufacture IJ19, IJ21, IJ23,packing density IJ25, IJ26 therefore low manufacturing cost Through Inkflow is through the ♦ Suitable for ♦ Pagewidth print ♦ Epson Stylusactuator actuator, which is not piezoelectric print heads require ♦Tektronix hot fabricated as part of heads several thousand meltpiezoelectric the same substrate as connections to drive ink jets thedrive transistors. circuits ♦ Cannot be manufactured in standard CMOSfabs ♦ Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqeous, Waterbased ink which ♦ Environmentally ♦ Slow drying ♦ Most existing ink dyetypically contains: friendly ♦ Corrosive jets water, dye, surfactant, ♦No odor ♦ Bleeds on paper ♦ All IJ series ink humectant, and ♦ Maystrikethrough jets biocide. ♦ Cockles paper ♦ Silverbrook, EP Modern inkdyes have 0771 658 A2 and high water-fastness, related patent lightfastness applications Aqueous, Water based ink which ♦ Environmentally ♦Slow drying ♦ IJ02, IJ04, IJ21, pigment typically contains: friendly ♦Corrosive IJ26, IJ27, IJ30 water, pigment, ♦ No odor ♦ Pigment may clog♦ Silverbrook, EP surfactant, humectant, ♦ Reduced bleed nozzles 0771658 A2 and and biocide. ♦ Reduced wicking ♦ Pigment may clog relatedpatent Pigments have an ♦ Reduced actuator applications advantage inreduced strikethrough mechanisms ♦ Piezoelectric ink- bleed, wicking and♦ Cockles paper jets strikethrough. ♦ Thermal ink jets (with significantrestrictions) Methyl MEK is a highly ♦ Very fast drying ♦ Odorous ♦ AllIJ series ink Ethyl volatile solvent used ♦ Prints on various ♦Flammable jets Ketone for industrial printing substrates such as (MEK)on difficult surfaces metals and plastics such as aluminum cans. AlcoholAlcohol based inks can ♦ Fast drying ♦ Slight odor ♦ All IJ series ink(ethanol, be used where the ♦ Operates at sub- ♦ Flammable jets2-butanol, printer must operate at freezing and temperatures belowtemperatures others) the freezing point of ♦ Reduced paper water. Anexample of cockle this is in-camera ♦ Low cost consumer photographicprinting. Phase The ink is solid at ♦ No drying time- ♦ High viscosity ♦Tektronix hot change room temperature, and ink instantly freezes ♦Printed ink melt piezoelectric (hot melt) is melted in the print on theprint medium typically has a ink jets head before jetting. ♦ Almost anyprint ‘waxy’ feel ♦ 1989 Nowak U.S. Pat. No. Hot melt inks are mediumcan be used ♦ Printed pages may 4,820,346 usually wax based, ♦ No papercockle ‘block’ ♦ All IJ series ink with a melting point occurs ♦ Inktemperature jets around 80° C. After ♦ No wicking may be above thejetting the ink freezes occurs curie point of almost instantly upon ♦ Nobleed occurs permanent magnets contacting the print ♦ No strikethrough ♦Ink heaters medium or a transfer occurs consume power roller. ♦ Longwarm-up time Oil Oil based inks are ♦ High solubility ♦ High viscosity:♦ All IJ series ink extensively used in medium for some this is asignificant jets offset printing. They dyes limitation for use in haveadvantages in ♦ Does not cockle ink jets, which improved paper usuallyrequire a characteristics on ♦ Does not wick low viscosity. Some paper(especially no through paper short chain and wicking or cockle). Oilmulti-branched oils soluble dies and have a sufficiently pigments arerequired. low viscosity. ♦ Slow drying Micro- A microemulsion is a ♦Stops ink bleed ♦ Viscosity higher ♦ All IJ series ink emulsion stable,self forming ♦ High dye than water jets emulsion of oil, water,solubility ♦ Cost is slightly and surfactant. The ♦ Water, oil, andhigher than water characteristic drop size amphiphilic soluble based inkis less than 100 nm, dies can be used ♦ High surfactant and isdetermined by ♦ Can stabilize concentration the preferred curvaturepigment suspensions required (around of the surfactant. 5%)

I claim:
 1. A method of manufacture of a drop on demand ink jet printhead arrangement including a series of nozzle chambers, said methodcomprising the steps of: (a) providing an initial semiconductor waferhaving an electrical circuitry layer and a buried epitaxial layer formedthereon; (b) etching a nozzle chamber cavity in said wafer. said etchingstopping substantially at said epitaxial layer; (c) depositing andetching a first layer having a high saturation flux density on saidelectrical circuitry layer to define a first magnetic plate; (d)depositing and etching an insulating layer on said first layer and saidelectrical circuitry layer, said etching including etching vias for asubsequent conductive layer; (e) depositing and etching a conductivelayer on said insulating layer in the form of a conductive coilconductively interconnected to said first layer; (f) depositing andetching a sacrificial material layer in the region of said firstmagnetic plate and said coil, said etching including defining aperturesfor a series of spring posts; (g) depositing and etching a second layerhaving a high saturation flux density so as to form an interconnectedsecond magnetic plate, series of attached springs and spring posts todefine an actuator for effecting ink ejection on demand; (h) etching theback of said wafer to said epitaxial layer; (i) etching an ink ejectionnozzle through said epitaxial layer interconnected with said nozzlechamber cavity; and (j) etching away any remaining sacrificial layers.2. A method as claimed in claim 1 wherein said step (f) furthercomprises etching cavities defining a series of spring posts and saidstep (g) includes forming a series of leaf springs interconnected withsaid second magnetic plate for resiliently biasing said magnetic platein a first direction.
 3. A method as claimed in claim 1 wherein saidconductive layer comprises substantially copper.
 4. A method as claimedin claim 1 further including the step of depositing corrosion barriersover portions of said arrangement so as to reduce corrosion effects. 5.method as claimed in claim 1 wherein the etching of layers includesetching vias so as to allow for the electrical interconnection ofportions of subsequent layers.
 6. A method as claimed in claim 1 whereinsaid magnetic flux material comprises substantially a cobalt nickel ironalloy.
 7. A method as claimed in claim 1 wherein said wafer comprises adouble side polished CMOS wafer.
 8. A method as claimed in claim 1wherein step (j) is also utilised to simultaneously separate said waferinto separate print heads.